How to: H2O - improved herbicides

For many herbicides, a lack of rainfall threatens to cause poor performance. Here are some tips to improve your herbicide performance using your existing irrigation system.

Apply enough water.
Most growers appreciate a nice rainfall the night after they finish applying soil-applied (pre-emergence) herbicides. Producers with irrigation can take advantage of their investment by making sure every irrigated field has optimum herbicide performance.

Commonly irrigated sandy loam soils of Indiana and Michigan need about a half inch of irrigation to wet the soil down to 5-6 inches. This amount most often is enough to incorporate soil-applied herbicides. Heavier loam soils may need 0.7 inch to 1.0 inch of water to wet the top 6 inches of soil to activate herbicides.

Follow the label.
Many herbicide labels have recommendations to use irrigation to improve performance or warnings to expect weed escapes if lack of rain leaves the herbicide incorporated.

An ounce of prevention’s worth a pound of cure.
Glyphosate-based herbicide labels often include the verbiage “apply to only actively-growing weeds.” Drought-stressed weeds have difficulty absorbing and translocating the active ingredient where it is needed to kill the plant.

In drought conditions, irrigating fields prior to post-emergence weed control applications can often improve performance.

Keep your system ready.
One of the excuses most often cited for not taking advantage of the option to irrigate to improve herbicides performance in dry conditions is that the irrigation system was not ready to run. Having the irrigation system ready to run when you plant can makes the difference between looking at a weed-free field that is primed for maximum yield potential or paying for post-emergence control and hoping it will work.

Information provided from Michigan State University Extension.

For more: www.msue.msu.edu.